How fast you cool or heat water depends upon the difference in temperatures inside and outside the vessel, the mass or volume of the water, the surface area of the vessel, and the thickness and conductivity of the material that the vessel is made with; the geometry of the vessel might be a factor insofar as it might affect conductive currents, but I think that's a non-issue for us. Of the materials that brewers use most often (I don't know about plastic buckets or conicals), the rank from best conductor to worst conductor is:
copper
aluminum
stainless steel
glass -- but you shouldn't be putting boiling water in a carboy anyway.

Regardless of what you use, I would just about guarantee you that it will not cool down enough in one hour unless you refrigerate it or use a cold water bath or something like that. And remember that if you intend to use this water for the dual purpose of diluting a concentrated boil and also cooling it down, you'll want that water to be as cold as you can get it. What's the rush in cooling boiled water? Crash cooling wort is another matter.

Well, I heated up the 3 gallons to 160-170 to sterilize the water. It then took a few hours to cool down, but it was good to go when my wort was ready. Today when I woke up the primary had some nice fermentation going on. Now I just have to wait and see how it turns out.